Rocking-type piston engine

ABSTRACT

Four pistons (20) are arranged offset from one another at angular spacings of 90° in a housing (10) having a cylindrical inner wall, and they are each supported to be pivotable about a piston axis (B) which is parallel to the housing axis (A). The pistons (20) are designed as two-armed levers whose arms are in rolling engagement with a respective adjacent piston arm so that four housing chambers (18) are defined in the housing (10) by a pair each of piston arms in rolling engagement with each other. Either a fuel-air mixture or air into which fuel is injected is processed in the housing chambers (18) according to the Otto or Diesel four stroke cycle, with the pistons (20) rocking back and forth like a balance. These rocking motions are converted into rotation of a central shaft (30) by cam followers (38) which roll off running surfaces (40) formed on the pistons (20).

The invention relates to a rocking-type piston engine, comprising

a housing in which a plurality of chambers are defined all around acentral housing axis between two end walls,

a plurality of pistons, each pivotable about a piston axis in parallelwith the housing axis and sealed with respect to both end walls,

a central shaft which is rotatable about the housing axis and in drivingconnection with the pistons, and

inlet and outlet passages for supply and discharge, respectively, of afluid into and out of the chambers of the housing.

In a known rocking piston engine of this kind (DE 23 63 077 B2) fourcylinder chambers are disposed all around the central axis of thehousing; they are each defined by a circular cylindrical wall portionand two planar side wall portions converging radially outwardly in anapex. Each of the four cylinder chambers is divided into two housingchambers by a plate-like piston which is pivotably supported in the areaof the apex. The total number of four pistons each are connected by acrank drive to a gear each meshing with a central gear fastened on thecentral shaft. In this manner the pivoting motions of the four pistonsare synchronized in such a way that each of them carries out windshieldwiper-like reciprocating movements during which it effects sealing withrespect to the two end walls and the circular cylindrical inner wallportion.

A similar arrangement comprising only three rocker pistons is known fromFR 800 753 A1.

The provision of the pistons in a rocking-type piston engine known fromDE 19 47 406 A1 is inverted radially outwardly as compared to those twoarrangements. In this case four pistons are supported closely adjacentone another at a central housing portion, and their radially outer edgeseach are movable back and forth in sealing fashion along a circularcylindrical outer housing wall portion, each of the pistons defining ahousing chamber together with each of the two adjacent pistons. Incontrast to the two rocking piston engines described previously, thereare no partitions here between adjacent pistons.

What all three known rocking piston engines described above have incommon is that good sealing between the paraxial radially outer (DE 2363 077 B1 and FR 800 753 A1) or radially inner (DE 19 47 406 A1) sealingedges of the pistons and the corresponding circular cylindrical housingwall portions is not obtainable unless the housing is machined true toshape and size in these areas and does not become distorted under theusual loads by the influence of forces or heat. Although a compensationof forces due to inertia of the first and higher orders which occur inoperation can be achieved, in principle, with the known rocking pistonengines including four equal rocking pistons, this is so only by way ofthe crank drives which connect the pistons to the central shaft. Thesegear connections, however, have an inherent, unavoidable rotationalelasticity so that the greatly varying forces acting on the individualpistons at any particular moment may cause vibrations of the gears and,being disturbing as such, these vibrations also may affect the massequilibrium.

It is, therefore, the object of the invention to provide a rocking-typepiston engine which is marked by improved cooperation of the individualpistons.

The object is met, in accordance with the invention, starting from arocking-type piston engine of the kind mentioned initially, in that

the pistons are embodied by two-armed levers whose arms each are insealing rolling engagement with a respective adjacent piston throughmeshing teeth, and

each housing chamber is defined by a pair of piston arms in rollingengagement.

The mutual sealing engagement between the piston arms greatlyfacilitates the seal between the pistons and the housing. Consequentlysufficient sealing effect is maintained even if the housing deformsunder thermal load. The forces to be transmitted for achieving completemass equilibrium are transmitted directly between the pistons and,therefore, largely without vibrations. While the meshing pistons rock inopposite senses, air or a fuel-air mixture can be compressed in thehousing chambers at any desired ratio so that the rocking piston engineaccording to the invention can be designed both as an Otto engine or aDiesel engine and can be operated at high thermodynamic efficiency withany desired liquid or gaseous fuels, such as hydrocarbons.

Advantageous further developments of the invention may be gathered fromthe subclaims.

An embodiment of the invention will be described in greater detailbelow, with reference to diagrammatic drawings, in which:

FIG. 1 shows a rocking-type piston engine, devised as a four stroke Ottoengine, in longitudinal section I-I according to FIG. 2;

FIG. 2 is the cross section II-II according to FIG. 1;

FIG. 3 is a cross section corresponding to FIG. 2 of a modifiedrocking-type piston engine;

FIG. 4 shows a cross section of another rocking-type piston engine,devised as a four stroke Otto engine, at the ignition time;

FIG. 5 shows a corresponding cross section, 30° after the ignition time;

FIG. 6 is the longitudinal section VI-VI of FIG. 5

FIG. 7 is the cross section VII-VII of FIG. 6;

FIGS. 8A-8H show cross sections of the rocking-type piston engineillustrated in FIGS. 1 to 7 at eight points in time which succeed eachother at intervals of 10°;

FIG. 9 is a cross section of another modified rocking-type pistonengine, likewise designed as a four stroke Otto engine; and

FIG. 10 is a cross section of a rocking-type piston engine designed as apump or compressor.

The rocking piston engine illustrated in FIGS. 1 and 2 comprises ahousing 10 with a central housing portion which forms a peripheral wall12 and two laterally integral housing portions which each present an endwall 14 with a respective extension 16 projecting annularly outwardly.The housing 10 is substantially rotationally symmetrical with respect toa central housing axis A; the peripheral wall 12 is substantially ofcircular cylindrical shape radially inwardly; and the end walls 14 aresubstantially planar axially inwardly. Four housing chambers 18, eachdefined by a pair of pistons in the interior of the housing 10, areoffset by 90° each with respect to one another.

The piston pairs are formed by a total of four double-armed, arcuatepistons 20, each having a part cylindrical bearing portion 22 at theirradially outer side for support in a complementary bearing 24 at theinside of the peripheral wall 12. Together with the correspondingbearing 24, the bearing portion 22 of each piston 20 defines a pistonaxis B about which the respective piston is pivotable. In the embodimentshown, the bearing portions 22 of the pistons 20 are convex and thebearings 24 at the peripheral wall 12 thus are concave. Yet an inversedesign is feasible as well.

Each of the pistons 20 is formed at the end of each of its two arms withteeth 26 and 28, respectively, engaging in complementary teeth 28 and26, respectively, of the adjacent piston 20. By these toothings 26 and28, the pistons 20 can roll off each other such that all the pistons canbe rocked back and forth only simultaneously and by the same angle,while adjacent pistons are rocking back and forth in oppositedirections, between end positions in which one arm each of each pistonabuts against the peripheral wall 12.

A central shaft 30 whose geometric axis coincides with the housing axisA extends through the housing 10. The central shaft 30 is supported in ashaft bearing 32 each in the two end walls 14 and comprises two paralleltransverse members 34 between the two end walls which members areintereconnected by a pair of bearing journals 36. The two bearingjournals 36 are disposed eccentrically with respect to the housing axisA, their axes C extending parallel to the housing axis A, diametricallyopposite each other.

A cam follower 38 in the form of a cylindrical roller is freelyrotatable on each of the two bearing journals 36. The cam followers 38are adapted to roll off running surfaces 40 at the radially inner sideof the pistons 20. In cross section the running surface 40 of eachindividual piston 20 is shaped approximately like a parabola whose axisintersects the corresponding piston axis B and whose smallest radius ofcurvature is slightly greater than half the outer diameter of the camfollowers 38.

The pistons 20 each have two parallel end surfaces 42 which are sealedagainst a respective one of the end walls 14 by an annular seal 44 eachand a radial seal 46 starting from the first mentioned seal. In fourregions located radially inside each of the four bearings 24, theannular seal 44 has the shape of a quarter of a circle each. Thesequarter circles are interconnected by a rectilinear portion each. Allthe seals 44 and 46 are embedded in grooves formed in the end walls 14.

An approximately semispherical combustion chamber 48 is defined at theradially outer side of each of the two arms of each piston 20. Thus twocombustion chambers 48 each are associated with each of the four housingchambers 18. Two spark plugs 50 project into each of the housingchambers 18 and are directed towards the centers of the twocorresponding combustion chambers 48.

Each combustion chamber 48 furthermore is connected by a pair of inletvalves 52 and a pair of outlet valves 54 to a pair of inlet passages 56and a pair of outlet passages 58, respectively. The inlet and outletvalves 52 and 54 are disposed in one each of the end walls 14 andcontrolled by a pair of cam discs 60 arranged substantially radiallyinside one each of the annular extensions 16, fastened on the centralshaft 30, and supported by an axial pressure bearing 62 each on ahousing cover 64 each.

Finally, one end of the central shaft 30 is connected to an ignitiondistributor 66. The other shaft end 68 has a multi-groove profile forconnection of an aggregate which is to be driven.

The rocking piston engine illustrated is intended to operate as a fourstroke Otto engine. Let us assume the left housing chamber 18 in FIG. 2and the two combustion chambers 48 communicating with it contained acompressed fuel-air mixture, the associated inlet and outlet valves 52and 54 were closed, and the central shaft 30 rotated in clockwise sense.Now, when the mixture in the two left combustion chambers 48 is ignited,the mutually engaged arms of the upper and lower left pistons 20 willrock towards the inside in the direction of the housing axis A. At thesame time, the two mutually engaged arms of the upper left and rightpistons 20 will rock upwardly, thereby compressing the fuel-air mixturein the upper housing chamber 18 whose inlet and outlet valves 52 and 54likewise are closed. At the same time, the mutually engaged arms of theright upper and lower pistons 20 will rock inwardly, whereby freshmixture, possibly precompressed, will flow into the right housingchamber 18 whose inlet valves 52 are open and whose outlet valves 54 areclosed. Again at the same time, the mutually engaged arms of the lowerright and left pistons 20 will rock outwardly so that previouslycombusted mixture will be ejected from the lower housing chamber 18whose inlet valves 52 are closed and whose outlet valves 54 are open.During this time the central shaft 30 carries out a revolution of 90° inclockwise sense.

The next ignition takes place in the upper housing chamber 18, and allthe processes described are repeated in housing chambers 18 which areoffset in clockwise sense by 90° with respect to the correspondinghousing chambers of the preceding cycle.

Thus four complete cycles of four strokes each take place during onefull revolution of the central shaft 30. During these operations theoverall center of gravity of all the moving parts always remains at thesame location D on the housing axis A. Consequently, a full static anddynamic equilibrium of masses is accomplished. The smooth running of themachine described above, therefore, is at least equivalent to that of areciprocating piston in-line engine comprising six cylinders.

In the case of the embodiment shown in FIG. 3 the pistons 20 each aresupported on a respective bearing journal 70 which is fastened in thetwo end walls 14 and has piston axis B as its geometric axis. Thebearing portions 22 according to FIG. 3 are sealed with respect to thehousing 10 by sealing strips 72 embedded in the housing in order toassure that the housing chambers 18 will be separated from one anotheralso if there is a relatively large clearance between the bearingportions and the housing. With the embodiment according to FIGS. 1 and2, on the other hand, the direct contact between the bearing portions 22and the corresponding bearings 24 is sufficient to keep the housingchambers 18 separated.

The embodiment according to FIG. 3 further differs from the oneillustrated in FIGS. 1 and 2 by the provision of only one spark plug 50in each housing chamber 18. The inlet and outlet valves 52 and 54 aredisposed radially and controlled by control shafts (not shown) which aredriven in conventional manner by the central shaft 30.

The bearing journals 70 in FIG. 3 may be replaced by shafts firmlyconnected to one each of the pistons 20 and driving the central shaft 30e.g. through gears and directional locking mechanisms or crank drives.In this event the transverse members 34, bearing journals 36, and camfollowers 38 can be dispensed with.

The embodiments presented in FIGS. 4 to 10 differ from FIGS. 1 to 3mainly by the following features:

The four pistons 20, again devised as double armed levers, each includea concave bearing portion 22 by which they are supported on a bearing 24each in the form of a part cylindrical sleeve. Each of these bearings 24is fastened on a bar 72 which extends parallel to the housing axis A andhas a part cylindrical outer surface 74 by which it is adapted to slidealong the peripheral wall 12 of the housing, being sealed in axialdirection by means of seals 76. The bearings 24 likewise extend insealing fashion up to the peripheral wall 12. A total of four bars 72are provided for the four pistons 20, and they are retained at one endeach by a ring 78 in offset relationship of 90° with respect to oneanother, while their other ends are held by a disc 80. Each bar 72 isfitted with clearance in radial outward direction, away from the housingaxis A.

The disc 80 is secured to the central shaft 30. The bars 72, the ring78, and the disc 80 form a kind of cage which rotates together with thecentral shaft 30. The bars 72 and the bearings 24 fixed upon them arepressed against the peripheral wall 12 of the housing by centrifugalforces, by virtue of the radial clearance mentioned, so that the fourhousing chambers 18 which take part in the rotation of the cage, justlike the pistons 20, are reliably sealed with respect to each other.

The cam followers 38 embodied by eccentric rollers having anapproximately drop-shaped outline are supported in the end walls 14 ofthe housing 10 by a pair of bearing journals 82 each. The runningsurfaces 40 with which the pistons 20 are formed each have an outline ofcircular arc shape, according to FIGS. 4 to 10, and the cam followers 38can roll off the same without slipping. According to FIGS. 4 to 10 eachof the cam followers 38 is connected firmly to a pinion 84 or made inone piece with the same, and each of these pinions meshes with anintermediate gear 86. Thus a total of four intermediate gears 86 areprovided which mesh with the teeth of a central gear 88 fastened on thecentral shaft 30 and having four times as many teeth as each of thepinions 84. The transmission ratio between the central shaft 30 and eachof the cam followers 38 is 1:4.

In agreement with FIGS. 1 to 3, an annular seal 44 each is disposed atthe end walls 14 of the housing 10 according to FIGS. 4 to 10. Thisseal, however, is circular and does not seal against the the pistons 20alone but also against the ring 78 or the disc 80.

In contrast to FIGS. 1 to 3, the embodiments shown in FIGS. 4 to 10 donot comprise a valve. According to FIGS. 4 to 9 the housing 10 includesonly one inlet passage 56 and one outlet passage 58, and these passagesare controlled directly by the pistons 20, in other words they areopened or blocked in accordance with the strokes. Moreover, according toFIGS. 4 to 9, there is only a single pair of spark plugs 50, and theyare disposed offset with respect to the inlet passage 56 and the outletpassage 58 by from 130° to 140° each, preferably 135° . Depending on theaxial length of the rocking piston engine, the two spark plugs 50illustrated can be replaced by a single one or supplemented by one orseveral more spark plugs.

The mode of operation of the rocking piston engine illustrated in FIGS.4 to 7, as a four stroke Otto engine, is shown in FIG. 8. FIG. 8Aconforms to FIG. 4 and illustrates the position of the movablestructural members at the ignition time. During this time, fuel-airmixture previously aspired and compressed is ignited in the lowerhousing chamber 18, while burnt mixture is displaced from the lefthousing chamber 18' through the outlet 92, fresh mixture is sucked intothe upper housing chamber 18" through the inlet 90, and mixture iscompressed in the right housing chamber 18'".

According to FIG. 8B the four pistons 20 together with the central shafthave rotated through 10° in clockwise sense, while the two cam followers38 have rotated through 40° each, likewise in clockwise sense. Inanalogous manner the rotation of the central shaft 30 with the pistons20 continues by 10° each and the rotation of the cam followers 38 by 40°each, according to FIGS. 8C to 8H, so that after one full four strokecycle which terminates when the position according to FIG. 8A isreached, the central shaft 30 and the pistons 20 will have rotatedtogether through 90°, while the cam followers 38 each will have carriedout one full revolution of 360° about its own stationary axis C.Therefore, four complete four stroke cycles take place during one fullrevolution of the central shaft 30.

The rocking piston engine illustrated in FIG. 9 and likewise designed asa four stroke, spark ignition engine differs from the one shown in FIGS.4 to 8 in that the ring 78 is additionally connected to the disc 80 byeight slender rods 90 against which the pistons 20 abut in theirterminal rocking positions so that they cannot contact the peripheralwall 12 of the housing 10. Moreover, the teeth 26 and 28 presented inFIGS. 4 to 8 and also in FIGS. 1 to 3 as substantially cylindrical orinvolute toothings extending across the entire axial width of thepistons 20 are replaced, according to FIG. 9, by teeth 26 and 28 whichare formed by individual semispherical projections and complementarydepressions which are offset with respect to one another in axial andradial directions.

With corresponding alterations made of their conventional structuralcomponents, the rocking piston engines illustrated and described abovealso can be operated as fuel injection Otto or Diesel engines, aspneumatic or hydraulic engines, or as a compressor or pump.

In the case of the rocking piston machine shown in FIG. 10, designed asa pump or compressor, the housing 10 includes two inlet passages 56 andtwo outlet passages 58 in its peripheral wall 12 which are disposed at90° spacings in such manner that each inlet passage 56 is followed by anoutlet passage 58 and vice versa. With this disposition of inlet andoutlet passages the rocking piston machine shown in FIG. 10 may operatealso as a pneumatic or hydraulic engine.

I claim:
 1. A rocking-type piston engine, comprisinga housing (10) inwhich a plurality of chambers (18) are defined all around a centralhousing axis (A) between two end walls (14), a plurality of pistons(20), each being pivotable about a piston axis (B), which is parallelwith the housing axis (A), and each being sealed with respect to bothend walls (14), a central shaft (30) which is rotatable about thehousing axis (A) and in driving connection with the pistons (20), andinlet and outlet passages (56, 58) for supply and discharge,respectively, of a fluid into and out of the chambers (18) of thehousing, characterized in that the pistons (20) are two-armed levers,each piston arm being in sealing rolling engagement with a respectiveadjacent piston arm through meshing teeth (26, 28), and each housingchamber (18) is defined by a pair of piston arms in rolling engagement.2. The rocking-type piston engine as claimed in claim 1, characterizedin that the pistons (20) each have a running surface (40) at the sidefacing the housing axis (A) along which surface an eccentric cam (38)connected to the central shaft (30) is movable such that a definedangular position of the central shaft (30) is associated with eachpiston position.
 3. The rocking-type piston engine as claimed in claim2, characterized in that the running surfaces (40) of adjacent pistons(20) line up with each other without any intermediate gaps at certainpiston positions.
 4. The rocking-type piston engine as claimed in claim2, characterized in that two cams (38) are connected to the centralshaft (30) and are disposed diametrically opposite each other withrespect to the housing axis (A).
 5. The rocking-type piston engine asclaimed in claim 3, characterized in that two cams (38) are connected tothe central shaft (30) and are disposed diametrically opposite eachother with respect to the housing axis (A).
 6. The rocking-type pistonengine as claimed in any one of claims 1 to 4 and 5, characterized inthat the pistons (20) are supported by a cage (72, 78, 80) revolvingtogether with the central shaft (30), and the housing (10) has at leastone inlet passage (56) and at least one outlet passage (58) which arecontrolled directly by the piston (20).
 7. The rocking-type pistonengine as claimed in claim 6, characterized in that two cams (38) areconnected to the central shaft (30) and are disposed diametricallyopposite each other with respect to the housing axis (A) and the cams(38) are eccentric rollers, each of which is rotatable about an axis (C)which is fixed with respect to the housing.
 8. The rocking-type pistonengine as claimed in claim 7, characterized in that the central shaft(30) is connected to each cam (38) by a gear train (84, 86, 88) having atransmission ratio of 1:4.
 9. The rocking-type piston engine as claimedin any one of claims 1 to 4 and 5, characterized in that two combustionchambers (48), each formed in a respective one of the two correspondingpistons (20), are associated with each housing chamber (18).
 10. Therocking-type piston engine as claimed in claim 9, characterized in thateach housing chamber (18) comprises two spark plugs (50), eachassociated with a respective one of the two corresponding combustionchambers (48).